Co-doping for fermi level control in semi-insulating Group III nitrides

ABSTRACT

Semi-insulating Group III nitride layers and methods of fabricating semi-insulating Group III nitride layers include doping a Group III nitride layer with a shallow level p-type dopant and doping the Group III nitride layer with a deep level dopant, such as a deep level transition metal dopant. Such layers and/or method may also include doping a Group III nitride layer with a shallow level dopant having a concentration of less than about 1×10 17  cm −3  and doping the Group III nitride layer with a deep level transition metal dopant. The concentration of the deep level transition metal dopant is greater than a concentration of the shallow level p-type dopant.

FIELD OF THE INVENTION

The present invention relates to semiconductor materials and, moreparticularly, to semi-insulating Group III nitride semiconductor layers.

BACKGROUND

Materials such as silicon (Si) and gallium arsenide (GaAs) have foundwide application in semiconductor devices for lower power and (in thecase of Si) lower frequency applications. These, more familiar,semiconductor materials may not be well suited for higher power and/orhigh frequency applications, however, because of their relatively smallbandgaps (e.g., 1.12 eV for Si and 1.42 for GaAs at room temperature)and/or relatively small breakdown voltages.

In light of the difficulties presented by Si and GaAs, interest in highpower, high temperature and/or high frequency applications and deviceshas turned to wide bandgap semiconductor materials such as siliconcarbide (2.996 eV for alpha SiC at room temperature) and the Group IIInitrides (e.g., 3.36 eV for GaN at room temperature). These materials,typically, have higher electric field breakdown strengths and higherelectron saturation velocities as compared to gallium arsenide andsilicon.

In fabricating high power and/or high frequency devices from Group IIInitrides, it may be beneficial to fabricate these devices on asemi-insulating Group III nitride layer, such as a semi-insulating GaNand/or AlInGaN layer. Insulating GaN layers have been fabricated bycarefully controlling the deposition conditions of undoped GaN.Insulating GaN layers have also been fabricated by doping the GaN layerswith Fe or C. While such techniques may produce a semi-insulating GroupIII nitride layer, variations between production runs may result indiffering insulating characteristics of the resulting layers.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide semi-insulating Group IIInitride semiconductor layers and methods of fabricating semi-insulatingGroup III nitride layers. In certain embodiments of the presentinvention, fabrication of a semi-insulating Group III nitride layerincludes doping a Group III nitride layer with a shallow level p-typedopant and doping the Group III nitride layer with a deep level dopant.The concentration of the deep level dopant is greater than aconcentration of the shallow level p-type dopant. In particularembodiments of the present invention, the deep level dopant is a deeplevel transition metal dopant. Additionally, the concentration of theshallow level dopant may be a net concentration.

In further embodiments of the present invention, the concentration ofthe shallow level p-type dopant is greater than a backgroundconcentration caused by defects and unintentional impurities in theGroup III nitride layer. The concentration of the shallow level p-typedopant may be less than about 1×10¹⁷ cm⁻³. The shallow level p-typedopant may be Mg and/or Zn and/or other p-type dopants. The deep leveltransition metal dopant may be Fe, Co, Mn, Cr, V and/or Ni and/or othertransition metal dopants. In particular embodiments of the presentinvention, the deep level transition metal dopant is Fe.

In additional embodiments of the present invention, a concentration ofthe shallow level p-type dopant is sufficient to cause a donor-likeenergy level of the deep level transition metal dopant to be a dominantenergy level of the deep level transition metal dopant.

In yet other embodiments of the present invention, the concentration ofthe deep level transition metal dopant is at least about three timesgreater than the concentration of the shallow level p-type dopant. Inparticular embodiments of the present invention, the concentration ofthe deep level transition metal dopant is greater than about 2×10¹⁷cm⁻³. In other embodiments of the present invention, the concentrationof the deep level transition metal dopant may be about 2×10 cm⁻³.Furthermore, doping with a shallow level p-type dopant and doping with adeep level transition metal may be carried out substantiallysimultaneously. For example, the Group III nitride layer may be grownutilizing chemical vapor deposition and doping with a shallow levelp-type dopant and doping with a deep level transition metal may becarried out during the chemical vapor deposition.

In still further embodiments of the present invention, a semi-insulatingGroup III nitride layer is fabricated by doping a Group III nitridelayer with a shallow level dopant having a concentration of less thanabout 1×10¹⁷ cm⁻³ and doping the Group III nitride layer with a deeplevel dopant, such as a deep level transition metal dopant. Theconcentration of the deep level dopant is greater than the concentrationof the shallow level dopant. In particular embodiments of the presentinvention, the concentration of the deep level transition metal dopantis greater than about 2×10¹⁷ cm⁻³. In other embodiments of the presentinvention, the concentration of the deep level transition metal dopantis about 2×10¹⁶ cm⁻³. The concentration of the shallow level dopant maybe greater than a background concentration caused by defects andunintentional impurities in the Group III nitride layer. Theconcentration of the shallow level dopant may be a net concentration.

In particular embodiments of the present invention, the shallow leveldopant is an n-type dopant. The deep level transition metal dopant maybe Fe, Co, Mn, Cr, V and/or Ni and/or other transition metal dopants.Furthermore, one of a p-type dopant and an n-type dopant may be selectedas the shallow level dopant so as to, respectively, cause a donor-likeenergy level of the deep level transition metal dopant to be a dominantenergy level of the deep level transition metal dopant or cause anacceptor-like energy level of the deep level transition metal dopant tobe a dominant energy level of the deep level transition metal dopant.

In additional embodiments of the present invention, a semi-insulatingsemiconductor material layer is provided by a Group III nitride layerincluding a shallow level p-type dopant and a deep level dopant, such asa deep level transition metal dopant. A concentration of the deep leveltransition metal dopant is greater than a concentration of the shallowlevel p-type dopant. The concentration of the shallow level p-typedopant may be greater than a background concentration caused by defectsand unintentional impurities in the Group III nitride layer. Theconcentration of the shallow level p-type dopant may be less than about1×10¹⁷ cm⁻³. The shallow level p-type dopant may be Mg and/or Zn and/orother p-type dopants. The deep level transition metal dopant may be Fe,Co, Mn, Cr, V and/or Ni and/or other transition metal dopants.Furthermore, a donor-like energy level of the deep level transitionmetal dopant may be a dominant energy level of the deep level transitionmetal dopant. In further embodiments of the present invention, theconcentration of the deep level transition metal dopant is at leastabout three times greater than the concentration of the shallow levelp-type dopant. In particular embodiments of the present invention, theconcentration of the deep level transition metal dopant is greater thanabout 2×10¹⁷ cm⁻³. In other embodiments of the present invention, theconcentration of the deep level transition metal dopant is about 2×10¹⁶cm⁻³.

In still further embodiments of the present invention, a semi-insulatingsemiconductor material layer is provided by a Group III nitride layerincluding a shallow level dopant having a concentration of less thanabout 1×10¹⁷ cm⁻³ and a deep level dopant, such as a deep leveltransition metal dopant. The concentration of the deep level transitionmetal dopant is greater than the concentration of the shallow leveldopant. The concentration of the shallow level dopant may be greaterthan a background concentration caused by defects and unintentionalimpurities in the Group III nitride layer. The shallow level dopant maybe an n-type dopant. The deep level transition metal dopant may be Fe,Co, Mn, Cr, V and/or Ni and/or other transition metal dopants. If theshallow level dopant is an n-type dopant, an acceptor-like energy levelof the deep level transition metal dopant may be a dominant energy levelof the deep level transition metal dopant. The concentration of the deeplevel transition metal dopant may be at least about three times greaterthan the concentration of the shallow level dopant. In particularembodiments of the present invention, the concentration of the deeplevel transition metal dopant is greater than about 2×10¹⁷ cm⁻³. Inother embodiments of the present invention, the concentration of thedeep level transition metal dopant is about 2×10¹⁶ cm⁻³.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating operations for fabricating asemi-insulating Group III nitride layer according to embodiments of thepresent invention.

FIG. 2 is a flowchart illustrating operations for fabricating asemi-insulating Group III nitride layer according to further embodimentsof the present invention.

FIG. 3 is a band diagram illustrating co-doping with a shallow acceptorto pin the Fermi level at a donor-like level of transition metal dopant.

FIG. 4 is a band diagram illustrating co-doping with a shallow donor topin the Fermi level at an acceptor-like level of transition metaldopant.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout. As will also be appreciatedby those of skill in the art, references herein to a layer formed “on” asubstrate or other layer may refer to the layer formed directly on thesubstrate or other layer or on an intervening layer or layers formed onthe substrate or other layer. As used herein the term “and/or” includesany and all combinations of one or more of the associated listed items.

Embodiments of the present invention may utilize co-doping of a GroupIII nitride layer with a shallow level dopant and a deep level dopant toprovide a predictable characteristic of a semi-insulating Group IIInitride layer. The term “semi-insulating” is used descriptively in arelative sense rather than in an absolute sense. In particularembodiments of the present invention, the semi-insulating Group IIInitride layer has a resistivity equal to or higher than about 1×10⁵ Ω-cmat room temperature.

Embodiments of the present invention may be particularly well suited foruse in nitride-based devices such as Group III-nitride based devices. Asused herein, the term “Group III nitride” refers to those semiconductingcompounds formed between nitrogen and the elements in Group III of theperiodic table, usually aluminum (Al), gallium (Ga), and/or indium (In).The term also refers to ternary and quaternary compounds such as AlGaNand AlInGaN. As is well understood by those in this art, the Group IIIelements can combine with nitrogen to form binary (e.g., GaN), ternary(e.g., AlGaN, AlInN), and quaternary (e.g., AlInGaN) compounds. Thesecompounds all have empirical formulas in which one mole of nitrogen iscombined with a total of one mole of the Group III elements.Accordingly, formulas such as Al_(x)Ga_(1-x)N where 0≦x≦1 are often usedto describe them.

Fabrication of materials according to embodiments of the presentinvention is illustrated in the flow chart of FIG. 1. As seen in FIG. 1,a Group III nitride layer is doped with a shallow level dopant at aconcentration of less than about 1×10¹⁷ cm⁻³ (block 100). The shallowlevel dopant may be an n-type dopant or a p-type dopant. For example,the shallow level dopant may be Si, Ge, O, Mg or Zn and/or other p-typeor n-type dopants. As used herein, a shallow level dopant refers to adopant that has an acceptor/donor energy level that is closer to theconduction or valence bands of the Group III nitride layer than theintended dominant level of the intentionally introduced deep leveldopant. In particular embodiments of the present invention, theacceptor/donor energy level of the shallow level dopant is within about0.3 eV of the conduction or valence band of the Group III nitride layer.

The Group III nitride layer is doped with a deep level dopant, such as atransition metal, so as to make the Group III nitride layersemi-insulating (block 110). The deep level transition metal dopant may,for example, be Fe, Co, Mn, Cr, V and/or Ni and/or other transitionmetal dopants. Other deep level dopants could also be utilized, forexample, C or a carbon complex. In particular embodiments of the presentinvention, the deep level transition metal dopant is Fe. As used herein,a deep level dopant refers to a dopant that has a large enough energyfrom the conduction or valence band so that at operating temperature, avery small number of free carriers would be in the conduction or valencebands. For example, a dopant that had an energy level that was greaterthan about 0.5 eV from the conduction band and contributed much lessthan 10¹⁴ cm⁻³ free carriers could be considered a deep level dopant.

Providing shallow level dopant concentrations of less than about 1×10¹⁷cm⁻³ may allow for production of a semi-insulating layer with lowerconcentrations of deep level dopants than may be needed with shallowlevel dopant concentrations of greater than about 1×10¹⁷ cm⁻³. Higherconcentrations of deep level dopant may be undesirable in certaincircumstances. For example, high concentrations of Fe may increasetrapping in comparison to lower concentrations of Fe. Thus, it may beadvantageous to provide a semi-insulating Group III nitride with lowerconcentrations of Fe.

FIG. 2 illustrates further embodiments of the present invention. As seenin FIG. 2, a Group III nitride layer is doped with a shallow levelp-type dopant (block 200). For example, the shallow level p-type dopantmay be Mg or Zn and/or other p-type dopants. The Group III nitride layeris also doped with a deep level dopant, such as a transition metal, soas to make the Group III nitride layer semi-insulating (block 210). Thedeep level transition metal dopant may, for example, be Fe, Co, Mn, Cr,V and/or Ni. Other deep level dopants could also be utilized, forexample, C or a carbon complex. In particular embodiments of the presentinvention, the deep level transition metal dopant is Fe.

Combinations of FIGS. 1 and 2 may also be provided where a shallow levelp-type dopant having a concentration of less than about 1×10¹⁷ cm⁻³ isprovided.

In the fabrication of a semi-insulating Group III nitride as illustratedin FIGS. 1 and 2, the concentration of the deep level dopant is greaterthan a concentration of the shallow level dopant. In particularembodiments of the present invention, the concentration of the deeplevel dopant is greater than the net concentration of the shallow leveldopant. As used herein, the term net concentration refers to theeffective concentration of the shallow level dopant. In certainembodiments of the present invention, the concentration of the deeplevel transition metal dopant is at least about three times theconcentration of the shallow level dopant. The particular concentrationlevel of the deep level dopant may depend on the device and/or the useof the device to be fabricated with the semi-insulating Group IIInitride layer. In particular embodiments of the present invention, thedeep level transition metal dopant may have a concentration of greaterthan about 2×10¹⁷ cm⁻³. Such a concentration may, for example, providehigher breakdown voltages in power devices fabricated with thesemi-insulating layer. In other embodiments of the present invention,the deep level transition metal dopant may have a concentration of about2×10¹⁶ cm⁻³. Such a concentration may, for example, provide higher powerdensities in power devices fabricated with the semi-insulating layer.

Furthermore, the concentration of the shallow level dopant should begreater than the background concentration caused by defects andunintentional impurities. In particular embodiments of the presentinvention, the concentration of the shallow level dopant is sufficientlygreat such that the position of the Fermi level of the material iscontrolled by the shallow level dopant in the absence of the deep leveldopant. However, the deep level dopant concentration is higher than thatof the shallow level dopant, so the Fermi level of the material ispinned at a level associated with the deep level dopant.

Depending on whether the shallow level dopant is p-type or n-type, adifferent character and energy level of the deep level dopant may beexpressed. The resistivity and trapping characteristics of the layer maybe affected by whether the shallow level dopant is p-type or n-type.Such may be the case, for example, if the deep level dopant has twoenergy levels where one energy level is donor-like and another isacceptor-like. Thus, for example, if the shallow level dopant is p-type,the dominant energy level of the deep level dopant may be donor-like.Such a case is illustrated in the band diagram of FIG. 3. If the shallowlevel dopant is n-type, the dominant energy level of the deep leveldopant may be acceptor-like. Such a case is illustrated in the banddiagram of FIG. 4. Thus, by selection of the shallow level dopant, thecharacteristics of the energy level of the co-doped layer may becontrolled to be either acceptor-like or donor-like. As used herein,acceptor-like refers to having an additional electron at a deep levelacceptor energy level, where the additional electron would not bepresent without the co-dopant and donor-like refers to having fewerelectrons at a deep level donor energy level, where the fewer electronswould be present without the co-dopant. Thus, by establishing the Fermilevel of the layer based on a combination of the deep level dopant andthe shallow level dopant, the characteristics of the resulting layer maybe more readily reproducible and the variations between processing runsmay be reduced, minimized and/or mitigated.

Additionally, the Group III nitride layer may be doped with the shallowand deep level dopants substantially simultaneously, for example, duringformation of the Group III nitride layer, such as by chemical vapordeposition. Formation of the Group III nitride layer may be provided byMOCVD or by other techniques known to those of skill in the art, such asMBE, HVPE, solution growth and/or high pressure growth. The doping ofthe Group III nitride layer may be incorporated as part of the growthprocess and/or may be provided as a separate process, for example, byimplantation after growth. For example, in particular embodiments of thepresent invention, the semi-insulating Group III nitride layer may befabricated using MOCVD while flowing both Cp₂Fe and Cp₂Mg (for p-typedopant) or SiH₄ (for n-type dopant). Alternatively or additionally,DeZn, GeH₄, Si₂H₆, H₂O and/or O₂ may also be used as a dopant source.Other sources could also be used.

In certain embodiments of the present invention, the semi-insulatingGroup III nitride layer is formed on a substrate on which nitride basedsemi-insulating layer is formed may be a silicon carbide substrateand/or layer and/or a Group III nitride substrate and/or layer and/or abuffer layer. Furthermore, the semi-insulating Group III nitride layermay be provided as a substrate. Accordingly, the term layer includeslayers and/or substrates. In particular embodiments of the presentinvention, the substrate on which the semi-insulating Group III nitridelayer is formed may be a semi-insulating silicon carbide (SiC) substratethat may be, for example, 4H polytype of silicon carbide. Other siliconcarbide candidate polytypes include the 3C, 6H, and 15R polytypes.

Silicon carbide has a much closer crystal lattice match to Group IIInitrides than does sapphire (Al₂O₃), which is a very common substratematerial for Group III nitride devices. The closer lattice match mayresult in Group III nitride films of higher quality than those generallyavailable on sapphire. Silicon carbide also has a very high thermalconductivity so that the total output power of Group III nitride deviceson silicon carbide is, typically, not as limited by thermal dissipationof the substrate as in the case of the same devices formed on sapphire.Appropriate SiC substrates are manufactured by, for example, Cree, Inc.,of Durham, N.C., the assignee of the present invention, and methods forproducing are described, for example, in U.S. Pat. Nos. Re. 34,861; U.S.Pat. Nos. 4,946,547; 5,200,022; and 6,218,680, the contents of which areincorporated herein by reference in their entirety. Similarly,techniques for epitaxial growth of Group III nitrides have beendescribed in, for example, U.S. Pat. Nos. 5,210,051; 5,393,993;5,523,589; and 5,292,501, the contents of which are also incorporatedherein by reference in their entirety.

Although silicon carbide and/or Group III nitrides may be used as asubstrate material, embodiments of the present invention may utilize anysuitable substrate, such as sapphire, aluminum nitride, silicon, GaAs,LGO, ZnO, LAO, InP and the like. In some embodiments, an appropriatebuffer layer also may be formed.

The Group III nitride layer may also be annealed, for example, to removenative defects and impurities, such as hydrogen, that may result fromthe co-doping of the semi-insulating Group III nitride layer. Forexample, a post growth nitrogen anneal could be performed on the GroupIII nitride layer.

In the drawings and specification, there have been disclosed typicalembodiments of the invention, and, although specific terms have beenemployed, they have been used in a generic and descriptive sense onlyand not for purposes of limitation.

1. A method of fabricating a semi-insulating Group III nitridesemiconductor layer, comprising: doping a Group III nitride layer with ashallow level p-type dopant; and doping the Group III nitride layer witha deep level dopant, wherein a concentration of the deep level dopant isgreater than a concentration of the shallow level p-type dopant.
 2. Themethod of claim 1, wherein the concentration of the deep level dopant isgreater than a net concentration of the shallow level p-type dopant. 3.The method of claim 1, wherein the concentration of the shallow levelp-type dopant is greater than a background concentration caused bydefects and unintentional impurities in the Group III nitride layer. 4.The method of claim 1, wherein the concentration of the shallow levelp-type dopant is less than about 1×10¹⁷ cm⁻³.
 5. The method of claim 1,wherein the shallow level p-type dopant comprises Mg and/or Zn.
 6. Themethod of claim 1, wherein the deep level dopant comprises a transitionmetal deep level dopant.
 7. The method of claim 6, wherein the deeplevel transition metal dopant comprises Fe, Co, Mn, Cr, V and/or Ni. 8.The method of claim 6, wherein the deep level transition metal dopantcomprises Fe.
 9. The method of claim 6, wherein a concentration of theshallow level p-type dopant is sufficient to cause a donor-like energylevel of the deep level transition metal dopant to be a dominant energylevel of the deep level transition metal dopant.
 10. The method of claim6, wherein the concentration of the deep level transition metal dopantis at least about three times greater than the concentration of theshallow level p-type dopant.
 11. The method of claim 6, wherein thedoping with a shallow level p-type dopant and the doping with a deeplevel transition metal are carried out substantially simultaneously. 12.The method of claim 6, further comprising growing the Group III nitridelayer utilizing chemical vapor deposition and wherein the doping with ashallow level p-type dopant and the doping with a deep level transitionmetal are carried out during the chemical vapor deposition.
 13. Themethod of claim 6, wherein the concentration of the deep leveltransition metal dopant is greater than about 2×10¹⁷ cm⁻³.
 14. Themethod of claim 6, wherein the concentration of the deep leveltransition metal dopant is about 2×10¹⁶ cm⁻³.
 15. A method offabricating a semi-insulating Group III nitride semiconductor layer,comprising: doping a Group III nitride layer with a shallow level dopanthaving a concentration of less than about 1×10¹⁷ cm⁻³; and doping theGroup III nitride layer with a deep level dopant, wherein aconcentration of the deep level dopant is greater than the concentrationof the shallow level dopant.
 16. The method of claim 15, wherein theconcentration of the shallow level dopant is a net concentration. 17.The method of claim 15, wherein the concentration of the shallow leveldopant is greater than a background concentration caused by defects andunintentional impurities in the Group III nitride layer.
 18. The methodof claim 15, wherein the shallow level dopant comprises an n-typedopant.
 19. The method of claim 15, wherein the deep level dopantcomprises a deep level transition metal dopant.
 20. The method of claim19, wherein the deep level transition metal dopant comprises Fe, Co, Mn,Cr, V and/or Ni.
 21. The method of claim 19, wherein the deep leveltransition metal dopant comprises Fe.
 22. The method of claim 19,further comprising selecting one of a p-type dopant and an n-type dopantas the shallow level dopant so as to, respectively, cause a donor-likeenergy level of the deep level transition metal dopant to be a dominantenergy level of the deep level transition metal dopant or cause anacceptor-like energy level of the deep level transition metal dopant tobe a dominant energy level of the deep level transition metal dopant.23. The method of claim 22, wherein the concentration of the deep leveltransition metal dopant is at least about three times greater than theconcentration of the shallow level dopant.
 24. The method of claim 19,wherein the doping with a shallow level dopant and the doping with adeep level transition metal are carried out substantiallysimultaneously.
 25. The method of claim 19, further comprising growingthe Group III nitride layer utilizing chemical vapor deposition andwherein the doping with a shallow level dopant and the doping with adeep level transition metal are carried out during the chemical vapordeposition.
 26. The method of claim 19, wherein the concentration of thedeep level transition metal dopant is greater than about 2×10¹⁷ cm⁻³.27. The method of claim 19, wherein the concentration of the deep leveltransition metal dopant is about 2×10¹⁶ cm⁻³.
 28. A semi-insulatingsemiconductor material layer, comprising a Group III nitride layerincluding a shallow level p-type dopant and a deep level dopant, whereina concentration of the deep level dopant is greater than a concentrationof the shallow level p-type dopant.
 29. The semiconductor material layerof claim 28, wherein the concentration of the shallow level p-typedopant is greater than a background concentration caused by defects andunintentional impurities in the Group III nitride layer.
 30. Thesemiconductor material layer of claim 28, wherein the concentration ofthe shallow level p-type dopant is less than about 1×10¹⁷ cm⁻³.
 31. Thesemiconductor material layer of claim 28, wherein the shallow levelp-type dopant comprises Mg and/or Zn.
 32. The semiconductor materiallayer of claim 28, wherein the concentration of the shallow level dopantis a net concentration.
 33. The semiconductor material layer of claim28, wherein the deep level dopant comprises a deep level transitionmetal dopant.
 34. The semiconductor material layer of claim 33, whereinthe deep level transition metal dopant comprises Fe, Co, Mn, Cr, Vand/or Ni.
 35. The semiconductor material layer of claim 33, wherein thedeep level transition metal dopant comprises Fe.
 36. The semiconductormaterial layer of claim 33, wherein a donor-like energy level of thedeep level transition metal dopant is a dominant energy level of thedeep level transition metal dopant.
 37. The semiconductor material layerof claim 33, wherein the concentration of the deep level transitionmetal dopant is at least about three times greater than theconcentration of the shallow level p-type dopant.
 38. The semiconductormaterial layer of claim 33, wherein the concentration of the deep leveltransition metal dopant is greater than about 2×10¹⁷ cm⁻³.
 39. Thesemiconductor material layer of claim 33, wherein the concentration ofthe deep level transition metal dopant is about 2×10¹⁶ cm⁻³.
 40. Asemi-insulating semiconductor material layer, comprising a Group IIInitride layer including a shallow level dopant having a concentration ofless than about 1×10¹⁷ cm⁻³ and a deep level dopant, wherein aconcentration of the deep level dopant is greater than the concentrationof the shallow level dopant.
 41. The semiconductor material layer ofclaim 40, wherein the concentration of the shallow level dopant isgreater than a background concentration caused by defects andunintentional impurities in the Group III nitride layer.
 42. Thesemiconductor material layer of claim 40, wherein the shallow leveldopant comprises an n-type dopant.
 43. The semiconductor material layerof claim 40, wherein the concentration of the shallow level dopant is anet concentration.
 44. The semiconductor material layer of claim 40,wherein the deep level dopant comprises a deep level transition metaldopant.
 45. The semiconductor material layer of claim 44, wherein thedeep level transition metal dopant comprises Fe, Co, Mn, Cr, V and/orNi.
 46. The semiconductor material layer of claim 44, wherein the deeplevel transition metal dopant comprises Fe.
 47. The semiconductormaterial layer of claim 44, wherein the shallow level dopant comprisesan n-type dopant and an acceptor-like energy level of the deep leveltransition metal dopant is a dominant energy level of the deep leveltransition metal dopant.
 48. The semiconductor material layer of claim44, wherein the concentration of the deep level transition metal dopantis at least about three times greater than the concentration of theshallow level dopant.
 49. The semiconductor material layer of claim 44,wherein the concentration of the deep level transition metal dopant isgreater than about 2×10¹⁷ cm⁻³.
 50. The semiconductor material layer ofclaim 44, wherein the concentration of the deep level transition metaldopant is about 2×10¹⁶ cm⁻³.